1. Field of the Invention
This invention relates to wheelchairs, particularly to powered wheelchairs, for use by handicapped and disabled persons, which can climb curbs.
2. Description of the Prior Art
As used herein, the term "conventional wheelchair", including plurals and variants thereof, denotes manually powered wheelchair apparati of the type generally disclosed in U.S. Pat. No. 3,953,054.
As used herein, the terms "conventional power wheelchair", "known power wheelchair" and "rear wheel drive power wheelchair", including plurals and variants thereof, denote powered wheelchair apparati of the type generally disclosed in U.S. Pat. No. 4,387,325.
Power wheelchairs are known and have been the subject of increasing development efforts to provide handicapped and disabled persons with independent mobility to assist them in leading more normal lives.
Power wheelchairs known heretofore resemble conventional, manual wheelchairs; many such power wheelchairs have merely been conventional wheelchairs equipped with motors. Use of such power wheelchairs sometimes results in the user feeling a stigma in that unthoughtful persons may view the power wheelchair user in a quizzical or even offensive manner.
Known power wheelchairs tend to be large and not particularly maneuverable. These power wheelchairs present difficulties for the user in navigating within conventional dwellings which have not been modified to accommodate such conventional power wheelchairs.
Typical rear wheel drive power wheelchairs, which are conventionally manual wheelchairs modified to be equipped with motors, have tuning circles of about 72 inches in diameter; whereas typical front wheel drive power wheelchairs known heretofore for the most part have turning circles in the neighborhood of 52 inches in diameter. These turning circles are too big for the user of a conventional power wheelchair to reverse the wheelchair direction by turning the wheelchair around within corridors or hallways of conventional office buildings or most homes.
Dual drive motor power wheelchairs are known; one is illustrated in U.S. Pat. No. 5,540,297. Other power wheelchairs are disclosed in U.S. Pat. Nos. 4,513,832; 4,538,857; 5,094,310; 5,145,020 and 5,366,037.
Forward or front wheel drive power wheelchairs are sold by Permobile, Inc. in Woburn, Mass. and have the driving wheels at the extreme forward end of the vehicle chassis thereby requiring substantial space in order to turn the power wheelchair. This large chair turning circle results from the axis of rotation of the chair, when turning, being at the mid-point of the drive wheel axes, which is at the extreme forward end of the chair. Hence, the radius of the chair turning circle cannot be substantially less than length of the chair chassis.
A forward wheel drive power wheelchair of the type sold by Permobile, Inc., with the drive wheels at the extreme forward end of the wheelchair chassis, is disclosed in a brochure entitled "Permobile Power Chair Empowering the Human Spirit" available from that company.
Wheelchairs having relatively large diameter forward wheels located under the central portion of the seat are known; one such wheelchair is disclosed in U.S. Pat. No. 4,538,857.
Known power and manual wheelchairs have significant difficulty in climbing curbs. Curbs may be six to eight inches or even higher. Curbs of this height present very substantial, often insurmountable obstacles for known power wheelchairs.